Fig. 4.

Epidermal cyst (24 MHz).

A. Intact (left cheek): grayscale ultrasonography with a color filter presents a well-defined, round-shaped, hypoechoic dermal and hypodermal structure (*). Posterior acoustic enhancement is noted at the bottom of the cyst (arrows). B. Ruptured (right dorsal forearm): color Doppler ultrasonography presents a partially lobulated hypoechoic dermal and hypodermal structure with some ill-defined areas at the bottom and a more intense hypoechoic band on the surface suggestive of a fragment of the capsule. The cyst generates a posterior acoustic enhancement artifact at the bottom (arrows). The hypervascularity in the periphery of the cyst should be noticed. There is also increased echogenicity of the surrounding hypodermis due to inflammation.